The majority of the young actors were modern Japanese that were recruited to play the WW2 generation. These modern Japanese knew absolutely nothing about their country's history and what it had done in the 1930s and 1940s in Asia. Moreover, they were astonished when it came to playing Japanese soldiers of the period and the beliefs they held.
The young Japanese actors were quick learners and did a credible job of acting in “Letters”, but to a man they kept repeating over and over there was so much the did not know about The Pacific War and the Iwo Jima battle. They returned home far wiser than when they came aboard to make this movie. To his credit, Eastwood honored them at a public presentation.
Wife and I visited Honolulu a few years ago as a retirement gift to ourselves.
On a tour of Pearl Harbor, we boated out to the Arizona Memorial and noted 75 percent of the folks on the boat were Japanese tourists.
I asked one young Japanese fellow why he wanted to see the sacred place. He responded that he and his wife wanted to see what their grandfathers had done; if it was really true. In so many words, they couldn’t believe it.